﻿// JavaScript Document

jQuery.fn.floatdiv=function(location){
//判断浏览器版本
var isIE6=false;
var Sys = {};
    var ua = navigator.userAgent.toLowerCase();
    var s;
    (s = ua.match(/msie ([\d.]+)/)) ? Sys.ie = s[1] : 0;
if(Sys.ie && Sys.ie=="6.0"){
   isIE6=true;
}
var windowWidth,windowHeight;//窗口的高和宽
//取得窗口的高和宽

if (self.innerHeight){
   windowWidth=self.innerWidth;
   windowHeight=self.innerHeight;
}else if(document.documentElement&&document.documentElement.clientHeight){
   windowWidth=document.documentElement.clientWidth;
   windowHeight=document.documentElement.clientHeight;
}else if(document.body){
   windowWidth=document.body.clientWidth;
   windowHeight=document.body.clientHeight;
}

return this.each(function(){
   var loc;//层的绝对定位位置
   if(location==undefined || location.constructor == String){
    switch(location){
     case("rightbottom")://右下角
      loc={right:"0px",bottom:"0px"};
      break;
     case("leftbottom")://左下角
      loc={left:"0px",bottom:"0px"};
      break; 
     case("lefttop")://左上角
      loc={left:"0px",top:"0px"};
      break;
     case("righttop")://右上角
      loc={right:"0px",top:"0px"};
      break;
     case("middletop")://居中置顶
      loc={left:windowWidth/2-$(this).width()/2+"px",top:"0px"};
      break;
     case("middlebottom")://居中置低
      loc={left:windowWidth/2-$(this).width()/2+"px",bottom:"0px"};
      break;
     case("leftmiddle")://左边居中
      loc={left:"0px",top:windowHeight/2-$(this).height()/2+"px"};
      break;
     case("rightmiddle")://右边居中
      loc={right:"0px",top:windowHeight/2-$(this).height()/2+"px"};
      break;
     case("middle")://居中
      var l=0;//居左
      var t=0;//居上
      l=windowWidth/2-$(this).width()/2;
      t=windowHeight/2-$(this).height()/2;
      loc={left:l+"px",top:t+"px"};
      break;
     default://默认为右下角
      location="rightbottom";
      loc={right:"0px",bottom:"0px"};
      break;
    }
   }else{
    loc=location;
   }
   var wrap=$("<div style='width:100%'></div>");
   /*fied ie6 css hack*/
   if(isIE6){wrap=$("<div style=\"top:expression(documentElement.scrollTop+documentElement.clientHeight-this.offsetHeight);\"></div>");}
  
   $("body").append(wrap);
   wrap.css(loc).css({position:"fixed",
    z_index:"999"});
   /*fied ie6 css hack*/
   if (isIE6)
   {
    wrap.css("position","absolute");
    $("body").css("background-attachment","fixed").css("background-image","url(n1othing.txt)");
   }
   //将要固定的层添加到固定层里
   $(this).appendTo(wrap);
});
};